hmm trying to control the pivot and transforms of the objects is a pain. Right now the simplest approach I can think of is to

1. duplicate the object
2. freeze the dups transforms
3. get the ymin of the bounding box for the dup = $lowest
4. delete the dup

Now with $lowest follow the algorithm as written. This seems to really be the cave man approach to the problem though as creating a duplicate and then deleting the duplicate for every object seems clumsy.